1. Field of the Invention
The present invention is related to a touch panel, and particularly to a touch panel with higher sensing sensibility.
2. Description of Related Art
FIG. 1 shows a conventional touch panel. To clearly illustrate the device design of the conventional touch panel, FIG. 1 only shows a portion of an enlarged sensing string and omits other possibly present film layers or devices. As shown in FIG. 1, a conventional touch panel 100 includes a plurality of first sensing string 120 and a plurality of second sensing string 140. More specifically, the first sensing string 120 extends in a first direction. Each of the first sensing string 120 is formed by serially connecting a plurality of first sensing pads 122 with a first bridge line 124. The second sensing string 140 extends in a second direction. Each of the second sensing string 140 is formed by serially connecting a plurality of second sensing pads 142 with a second bridge line 144. The first sensing pads 122 and the second sensing pads 142 can constitute a sensing array to achieve surface sensing.
When a user touches the touch panel 100 with a finger, the first sensing string 120 and the second sensing string 140 of the touch panel 100 would cause variation in capacitance on a position where the finger touches. Afterwards, the variation in capacitance is converted into a control signal to be transmitted to a control circuit board and calculated to obtain a result. Thereafter, a proper instruction according to the result is outputted to operate an electronic device. However, an area where the first bridge line 124 and the second bridge line 144 are intersected has a greater parasitic capacitance. In comparison with the parasitic capacitance, the variation in capacitance caused by the user touching the touch panel 100 is probably not sufficiently significant and thus is disadvantageous to calculation of a control circuit.
Generally, a line width of the first bridge line 124 or the second bridge line 144 is about 40 μm-70 μm. In order to reduce the parasitic capacitance, the line widths of the first bridge line 124 and the second bridge line 144 can be reduced in the intersection area of the first bridge line 124 and the second bridge line 144. Nevertheless, the first sensing pads 122, the second sensing pads 142, the first bridge line 124, and the second bridge line 144 are all fabricated by transparent conductive materials. If the line widths of the first bridge line 124 and the second bridge line 144 are reduced, the impedance of the bridge line will increase, which in turn is disadvantageous to touch sensing signal transmission.